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Non-retained expert depositions depend on how and when the witness formed the opinions and whether the witness was disclosed as a testifying expert. This article explains Rule 26 disclosure and compensation requirements, Rule 45 protections for unretained nonparties, and the risks of compelling new expert analysis or exceeding the disclosed testimony.
This issue can arise when a key professional knows something important about the case, but no one hired that person as a litigation expert. The witness may be a treating physician, engineer, investigator, accountant, technical employee, or another professional whose opinions came from direct involvement in the facts.
The practical question is this: did the opinion come from ordinary work, treatment, or firsthand involvement, or was it created for the lawsuit?
That distinction can affect disclosure duties, deposition rights, witness fees, subpoena limits, and exclusion risk. A non-retained expert disclosed by a party under Rule 26(a)(2)(C) may generally be deposed if the opinions may be presented at trial. An unretained nonparty professional subpoenaed for expert opinion testimony may receive stronger protection under Rule 45, especially when the subpoena seeks new expert opinions or expert analysis rather than firsthand factual testimony.
This guide explains when non-retained experts may be deposed, when Rule 45 protects unretained expert opinions, and what attorneys should consider before relying on or challenging this testimony.
A non-retained expert is a witness with specialized knowledge who was not hired or specially employed to provide expert testimony, but who may still offer expert opinions if properly disclosed. In many cases, the witness formed those opinions through ordinary professional work before litigation, not because counsel retained the witness to analyze the case.
Common examples include:
A party still must disclose the witness if the witness may offer expert opinion testimony at trial. Rule 26(a)(2)(C) requires the party to identify the subject matter of the expected testimony and provide a summary of the expected facts and opinions.
The label “non-retained” is helpful, but it is not enough by itself. Courts often look at when the opinion was formed, why it was formed, and whether the witness is being asked to provide litigation-driven expert work.
Rule 26(a)(2)(B) applies to experts retained or specially employed to provide expert testimony, as well as party employees whose duties regularly involve giving expert testimony. These experts must provide a detailed written report that includes their opinions, the facts or data they considered, exhibits, qualifications, publications, prior testimony, and compensation.
Non-retained experts usually do not need that full written report. But if the witness was specially retained or employed for the case, or performs the kind of additional litigation-driven analysis described below, the full Rule 26(a)(2)(B) requirements may apply regardless of how the party labeled the witness.
One major risk is classifying the witness too loosely. A party may call a witness non-retained, but if the witness developed opinions for litigation or performed new analysis requested by counsel, the court may require a full Rule 26(a)(2)(B) report or limit the testimony.
A treating physician is a common example. The physician may testify as a non-retained expert about opinions formed during treatment. But if counsel later asks that physician to review attorney-selected materials outside the treatment process and form new causation opinions for trial, the testimony can move beyond Rule 26(a)(2)(C).
The safer approach is usually to define the witness’s role early and make sure the disclosure matches the actual source and scope of the opinions.
This issue can arise when a key professional knows something important about the case, but no one hired that person as a litigation expert. The witness may be a treating physician, engineer, investigator, accountant, technical employee, or another professional whose opinions came from direct involvement in the facts.
The practical question is this: did the opinion come from ordinary work, treatment, or firsthand involvement, or was it created for the lawsuit?
That distinction can affect disclosure duties, deposition rights, witness fees, subpoena limits, and exclusion risk. A non-retained expert disclosed by a party under Rule 26(a)(2)(C) may generally be deposed if the opinions may be presented at trial. An unretained nonparty professional subpoenaed for expert opinion testimony may receive stronger protection under Rule 45, especially when the subpoena seeks new expert opinions or expert analysis rather than firsthand factual testimony.
This guide explains when non-retained experts may be deposed, when Rule 45 protects unretained expert opinions, and what attorneys should consider before relying on or challenging this testimony.
A non-retained expert is a witness with specialized knowledge who was not hired or specially employed to provide expert testimony, but who may still offer expert opinions if properly disclosed. In many cases, the witness formed those opinions through ordinary professional work before litigation, not because counsel retained the witness to analyze the case.
Common examples include:
A party still must disclose the witness if the witness may offer expert opinion testimony at trial. Rule 26(a)(2)(C) requires the party to identify the subject matter of the expected testimony and provide a summary of the expected facts and opinions.
The label “non-retained” is helpful, but it is not enough by itself. Courts often look at when the opinion was formed, why it was formed, and whether the witness is being asked to provide litigation-driven expert work.
Rule 26(a)(2)(B) applies to experts retained or specially employed to provide expert testimony, as well as party employees whose duties regularly involve giving expert testimony. These experts must provide a detailed written report that includes their opinions, the facts or data they considered, exhibits, qualifications, publications, prior testimony, and compensation.
Non-retained experts usually do not need that full written report. But if the witness was specially retained or employed for the case, or performs the kind of additional litigation-driven analysis described below, the full Rule 26(a)(2)(B) requirements may apply regardless of how the party labeled the witness.
One major risk is classifying the witness too loosely. A party may call a witness non-retained, but if the witness developed opinions for litigation or performed new analysis requested by counsel, the court may require a full Rule 26(a)(2)(B) report or limit the testimony.
A treating physician is a common example. The physician may testify as a non-retained expert about opinions formed during treatment. But if counsel later asks that physician to review attorney-selected materials outside the treatment process and form new causation opinions for trial, the testimony can move beyond Rule 26(a)(2)(C).
The safer approach is usually to define the witness’s role early and make sure the disclosure matches the actual source and scope of the opinions.
Usually, yes, if the witness has been identified as an expert whose opinions may be presented at trial, subject to the scheduling order and court-imposed discovery limits. Rule 26(b)(4)(A) generally allows the opposing party to depose any expert whose opinions may be presented at trial.
For retained experts, the deposition usually happens after the written report is served. For non-retained experts, deposition timing usually depends on Rule 26(a)(2)(C) disclosures, the scheduling order, local rules, and any limits set by the court.
The party seeking expert discovery should also be prepared to pay a reasonable fee for the expert’s time under Rule 26(b)(4)(E), unless manifest injustice would result. Even when the deposition is allowed, courts may still manage the scope, timing, burden, and compensation.
Rule 45 becomes important when a party subpoenas an unretained nonparty professional who has not been disclosed as a testifying expert for either side.
The rule protects unretained experts from subpoenas that demand expert opinions or information that does not describe specific occurrences in dispute and results from study not requested by a party. In practical terms, Rule 45 helps prevent a party from forcing an unwilling nonparty professional to create expert opinions for litigation.
A court may still order appearance or production if the serving party shows:
A subpoena seeking firsthand facts or previously formed opinions is usually on firmer ground than one asking an unwilling nonparty to create new expert analysis. Rule 45 itself supports resistance to subpoenas that ask an unwilling nonparty to study new materials, perform new testing, or develop opinions specifically for the litigation. Courts applying Rule 45(d)(3)(B)(ii) regularly distinguish between requests for facts a witness already knows and demands for new expert analysis the witness has never done.
The key cases focus less on the witness’s title and more on the witness’s involvement in the facts and how, when, and why the opinion was formed.
In Kaufman v. Edelstein, the Second Circuit addressed a government subpoena compelling two computer industry experts to testify in a major antitrust case. The court upheld the subpoenas and held that experts have no general privilege to refuse to testify. At the same time, the court identified factors that remain relevant when evaluating whether compelling testimony is appropriate: the burden on the witness, whether comparable testimony could be obtained elsewhere, and the distinction between asking a witness to restate opinions already formed versus requiring the witness to perform new expert work for the litigation. Courts and commentators have drawn on those considerations in later cases, even though the ultimate ruling in Kaufman favored compelling the testimony.
In Downey v. Bob’s Discount Furniture Holdings, Inc., the First Circuit treated an exterminator’s opinions as non-retained expert testimony because they came from firsthand involvement, not litigation retention.
In Goodman v. Staples The Office Superstore, LLC, the Ninth Circuit explained that treating physicians generally avoid full Rule 26(a)(2)(B) reports only for opinions formed during treatment. Opinions formed later for litigation may require a full report.
In Macchia v. Landline Trans, LLC, a district court treated timing and the circumstances of treatment as important when evaluating treating physician causation testimony. The key question was whether the opinion came from treatment or from litigation preparation.
Together, these cases point to the same practical lesson: the witness’s title does not control. The source, timing, and purpose of the opinion matter.
If a treating physician or technical participant will offer Rule 702 opinion testimony, identify the witness and provide the required Rule 26(a)(2)(C) summary. A vague disclosure can invite challenges and may give the court a reason to limit the testimony later.
Keep non-retained expert testimony tied to firsthand involvement, treatment, investigation, or ordinary professional work. If the testimony depends on new analysis, litigation-driven review, or trial-specific opinions, the witness may need to be treated as a retained expert.
A subpoena for facts is different from a subpoena demanding expert opinions from an unwilling nonparty professional. Before serving a subpoena, attorneys should consider whether they are seeking factual testimony or asking the witness to perform new expert work.
Be prepared to address compensation early. Rule 26 generally requires reasonable payment for time spent responding to expert discovery. Under Rule 45, a court may also require reasonable compensation when ordering compliance from an unretained expert.
Late or incomplete disclosures can lead to exclusion unless the failure was substantially justified or harmless. This can be a serious problem when the witness is central to causation, damages, standard of care, technical responsibility, or another disputed issue.
Scheduling orders, local rules, and judge-specific discovery limits may affect when a non-retained expert can be deposed and how broad the questioning may be. Reviewing those limits before serving notices or subpoenas can help prevent avoidable disputes.
Can a non-retained expert be forced to testify at deposition?
Sometimes. If the witness has been disclosed as a testifying expert, Rule 26 generally allows a deposition. But an unretained nonparty professional subpoenaed for expert opinion testimony may receive stronger protection under Rule 45, especially when the subpoena seeks new expert work rather than firsthand factual testimony.
Does a non-retained expert need a written report?
Usually no. Rule 26(a)(2)(C) generally requires the subject matter of the testimony and a summary of facts and opinions. But if the opinions were formed for litigation or depend on litigation-driven analysis, a full Rule 26(a)(2)(B) report may be required.
Are treating physicians non-retained experts?
Often, yes, but the scope matters. Treating physicians may be treated as non-retained experts when their opinions were formed during diagnosis, treatment, or related care. Opinions created later for litigation may require a full expert report.
Can a court exclude a non-retained expert?
Yes. Courts may limit or exclude testimony for inadequate disclosures, late disclosures, improper classification, or opinions that go beyond the disclosed scope.
Must a non-retained expert be paid for deposition time?
In many expert discovery situations, yes. Rule 26 generally requires reasonable compensation for expert discovery time unless manifest injustice would result. Under Rule 45, courts may also require reasonable compensation when ordering an unretained expert to comply with a subpoena.
Usually, yes, if the witness has been identified as an expert whose opinions may be presented at trial, subject to the scheduling order and court-imposed discovery limits. Rule 26(b)(4)(A) generally allows the opposing party to depose any expert whose opinions may be presented at trial.
For retained experts, the deposition usually happens after the written report is served. For non-retained experts, deposition timing usually depends on Rule 26(a)(2)(C) disclosures, the scheduling order, local rules, and any limits set by the court.
The party seeking expert discovery should also be prepared to pay a reasonable fee for the expert’s time under Rule 26(b)(4)(E), unless manifest injustice would result. Even when the deposition is allowed, courts may still manage the scope, timing, burden, and compensation.
Rule 45 becomes important when a party subpoenas an unretained nonparty professional who has not been disclosed as a testifying expert for either side.
The rule protects unretained experts from subpoenas that demand expert opinions or information that does not describe specific occurrences in dispute and results from study not requested by a party. In practical terms, Rule 45 helps prevent a party from forcing an unwilling nonparty professional to create expert opinions for litigation.
A court may still order appearance or production if the serving party shows:
A subpoena seeking firsthand facts or previously formed opinions is usually on firmer ground than one asking an unwilling nonparty to create new expert analysis. Rule 45 itself supports resistance to subpoenas that ask an unwilling nonparty to study new materials, perform new testing, or develop opinions specifically for the litigation. Courts applying Rule 45(d)(3)(B)(ii) regularly distinguish between requests for facts a witness already knows and demands for new expert analysis the witness has never done.
The key cases focus less on the witness’s title and more on the witness’s involvement in the facts and how, when, and why the opinion was formed.
In Kaufman v. Edelstein, the Second Circuit addressed a government subpoena compelling two computer industry experts to testify in a major antitrust case. The court upheld the subpoenas and held that experts have no general privilege to refuse to testify. At the same time, the court identified factors that remain relevant when evaluating whether compelling testimony is appropriate: the burden on the witness, whether comparable testimony could be obtained elsewhere, and the distinction between asking a witness to restate opinions already formed versus requiring the witness to perform new expert work for the litigation. Courts and commentators have drawn on those considerations in later cases, even though the ultimate ruling in Kaufman favored compelling the testimony.
In Downey v. Bob’s Discount Furniture Holdings, Inc., the First Circuit treated an exterminator’s opinions as non-retained expert testimony because they came from firsthand involvement, not litigation retention.
In Goodman v. Staples The Office Superstore, LLC, the Ninth Circuit explained that treating physicians generally avoid full Rule 26(a)(2)(B) reports only for opinions formed during treatment. Opinions formed later for litigation may require a full report.
In Macchia v. Landline Trans, LLC, a district court treated timing and the circumstances of treatment as important when evaluating treating physician causation testimony. The key question was whether the opinion came from treatment or from litigation preparation.
Together, these cases point to the same practical lesson: the witness’s title does not control. The source, timing, and purpose of the opinion matter.
If a treating physician or technical participant will offer Rule 702 opinion testimony, identify the witness and provide the required Rule 26(a)(2)(C) summary. A vague disclosure can invite challenges and may give the court a reason to limit the testimony later.
Keep non-retained expert testimony tied to firsthand involvement, treatment, investigation, or ordinary professional work. If the testimony depends on new analysis, litigation-driven review, or trial-specific opinions, the witness may need to be treated as a retained expert.
A subpoena for facts is different from a subpoena demanding expert opinions from an unwilling nonparty professional. Before serving a subpoena, attorneys should consider whether they are seeking factual testimony or asking the witness to perform new expert work.
Be prepared to address compensation early. Rule 26 generally requires reasonable payment for time spent responding to expert discovery. Under Rule 45, a court may also require reasonable compensation when ordering compliance from an unretained expert.
Late or incomplete disclosures can lead to exclusion unless the failure was substantially justified or harmless. This can be a serious problem when the witness is central to causation, damages, standard of care, technical responsibility, or another disputed issue.
Scheduling orders, local rules, and judge-specific discovery limits may affect when a non-retained expert can be deposed and how broad the questioning may be. Reviewing those limits before serving notices or subpoenas can help prevent avoidable disputes.
Can a non-retained expert be forced to testify at deposition?
Sometimes. If the witness has been disclosed as a testifying expert, Rule 26 generally allows a deposition. But an unretained nonparty professional subpoenaed for expert opinion testimony may receive stronger protection under Rule 45, especially when the subpoena seeks new expert work rather than firsthand factual testimony.
Does a non-retained expert need a written report?
Usually no. Rule 26(a)(2)(C) generally requires the subject matter of the testimony and a summary of facts and opinions. But if the opinions were formed for litigation or depend on litigation-driven analysis, a full Rule 26(a)(2)(B) report may be required.
Are treating physicians non-retained experts?
Often, yes, but the scope matters. Treating physicians may be treated as non-retained experts when their opinions were formed during diagnosis, treatment, or related care. Opinions created later for litigation may require a full expert report.
Can a court exclude a non-retained expert?
Yes. Courts may limit or exclude testimony for inadequate disclosures, late disclosures, improper classification, or opinions that go beyond the disclosed scope.
Must a non-retained expert be paid for deposition time?
In many expert discovery situations, yes. Rule 26 generally requires reasonable compensation for expert discovery time unless manifest injustice would result. Under Rule 45, courts may also require reasonable compensation when ordering an unretained expert to comply with a subpoena.
Expert Witness Guides
Expert Witness Guides